How do you calculate pressure drop in a Cv?
The basic valve sizing equation Q = Cv√∆P can be used to calculate pressure drop, flow rate, or the flow coefficient. For solutions other than water, a correction for a difference in specific gravity of the solution is necessary. This revised formula would be: Q = Cv[√∆P/Sg] with Sg = specific gravity of the liquid.
What is the pressure drop across a valve?
Pressure drop, or pressure loss, is the difference in pressure as measured between two points in a pipe with flowing fluid. Specific to control valves, it is the difference between the inlet pressure and outlet pressure. This pressure differential or Delta P is the inlet minus the outlet pressure.
How do you calculate valve Cv?
Cv by definition is the number of gallons per minute (GPM) a valve will flow with a 1 psi pressure drop across the valve. For example a valve with a Cv of 10 will flow 10 GPM with a 1 psi pressure drop. The formula used to select the valve Cv with the specified differential pressure is: Cv=GPM/((SQ RT(∆P)).
What is Cv value of valve?
What is Cv value? The valve flow coefficient according to the JIS standard, represents the flow capacity in US gallons/minute of 60° F pure water when it is flowing through the valve with a pressure difference of 1 psi at the specified travel (operation range).
Is valve Cv dimensionless?
CV: The Flow Coefficient, CV, is a dimensionless value that relates to a valve’s flow capacity. Its most basic form is Q=Flow rate and ∆P=pressure drop across the valve.
What is difference between Cv and KV in control valve?
Kv is the flow coefficient in metric units. Cv is the flow coefficient in imperial units. It is defined as the flow rate in US Gallons per minute [gpm] of water at a temperature of 60 fahrenheit with a pressure drop across the valve of 1 psi.
How to describe pressure drop across a valve?
Pressure drop across a valve is described by the valve’s Cv Flow coefficient. Cv has units of gpm/ (psi)^0.5, where gpm is flowrate in gallons/minute and psi is the differential pressure across the valve in psi.
How to calculate pressure drop With Cv flow coefficients?
With a known Cv flow coefficient the above formula can be re-arranged to calculate the pressure loss for a particular flow rate thus: The pressure loss through a fitting or valve may also be calculated from: Thus a 1.0 psi pressure drop is equivalent to 2.31 ft head of water at Normal Temperature & Pressure (NTP) or 62.3 lbs/ft 3.
What is the CV of an oversized valve?
An oversized valve operates more frequently at lower openings with increased dead band as result. For liquids the flow coefficient – Cv -is expressed with water flow capacity in gallons per minute (GPM) of 60oF with pressure drop 1 psi (lb/in2).
How to calculate pressure loss using the C V method?
Calculation of Pressure Loss using the C v Method A C v value is defined as the rate of flow of water in US gallons per Minute at 60°F at a pressure drop of 1 psi across the equipment. C v relates to pressure drop and flowrate via the following expression (imperial units): displaystyle C_v = Q sqrt {frac {SG} {Delta P}} C v